As has been said, your gun is a "Named Model", before model numbers were assigned in 1957, known as the "Military & Police" or M&P. The serial number places it toward the end of the 1954-1956 serial range, probably late 1955 to mid 1956. The front sight was changed from half-round to the ramped style yours has in 1952, so yours is absolutely correct
If you are really curious you could request a Factory Letter, but since this is the most common model S&W ever made, several million, it is hardly worth the cost!